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Estimating Population Size of Maryland’s Black
Bears
using Hair Snaring and DNA Analysis
Abstract: Black bear (Ursus americanus) populations have expanded
in Maryland since the late 1970s. Previous attempts to estimate bear numbers
have been hampered by access to private land and manpower shortages. The
development of hair snaring techniques, coupled with genetic fingerprinting,
provides a more efficient technique than traditional mark-recapture methods to
estimate black bear numbers in western Maryland. In May-June 2000, we
established 108 grids throughout occupied bear range in Garrett and western
Allegany counties in western Maryland. We established hair traps in each grid
for 4 week-long sampling periods. Hair samples that were snagged on barbed
wire were collected after each sampling period and kept for DNA analysis. We
subjected 330 hair samples to DNA analysis, and identified 92 individual
bears. We identified 45 males and 43 females, and the gender of an additional
4 bears could not be determined. We used Program CAPTURE to estimate the bear
population in western Maryland, and a total of 227 bears (95% C.I. 166-337)
were estimated to occupy the 2,152 km² area, 10.5 bears/100km2 (95%
C.I. 7.7-15.7). We found this technique to be more practical for estimating
bear numbers in western Maryland than the traditional mark-recapture technique
of running trap lines. Costs were substantially less per bear marked in 2000
than previous attempts.
Estimating Maryland's Black Bear Population. Bittner et al.
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